A solid material that was known to contain only cations of the aluminum-nickel group dissolved in HCl to give a green solution. The addition of NH4Cl and excess NH4OH gave a green precipitate, and the addition of (NH4)2S gave a black precipitate. The total precipitate was dissolved in HCl + HNO3. When the solution thus formed was treated with excess NaOH followed by H2O2, a colorless solution and a reddish brown precipitate were formed. The precipitate was found to be soluble in HCl, H2SO4, or HNO3. Which cations are present, possibly present, or absent?